JPH11279116A - Production of dialkyl oxalate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a dialkyl oxalate, capable of obtaining a dialkyl oxalate while reutilizing carbon monooxide occured in any other reaction, especially ionic halide-containing carbon monooxide without giving a bad influence on the reaction. SOLUTION: This method comprises (A) forming a dialkyl oxalate and nitrogen monooxide by reacting monooxide with an alkyl nitrile in a reactor 1, (B) separating the resultant product into a dialkyl oxalate-containing condensate and a nitrogen monooxide-containing non-condensed gas in a condenser 2, (C) regenerating the alkyl nitrite by contacting the non-condensed gas with molecular oxygen and an alkyl alcohol while feeding ionic halide-containing carbon monooxide treated with an alkali in a regenerating tower 3 and (D) feeding the regenerated gas and carbon monooxide into the reactor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a dialkyl oxalate by reacting carbon monoxide with an alkyl nitrite, and more particularly to a method for producing oxalic acid by effectively utilizing carbon monoxide produced by other reactions. The present invention relates to a method for producing a dialkyl. Dialkyl oxalate is a compound useful as oxalic acid, oxamide, glycolic acid, a raw material for pharmaceutical synthesis, and the like.

[0002]

2. Description of the Related Art A method for producing a dialkyl oxalate from carbon monoxide and an alkyl nitrite is disclosed in Japanese Patent Publication No. 61-6057.
JP, JP-B-61-26977, JP-B-57-
It is disclosed in, for example, Japanese Patent Publication No. 30095. However, in these known documents, a dialkyl oxalate is produced by effectively utilizing carbon monoxide produced by another reaction, particularly carbon monoxide containing a decomposable halogen compound without affecting the reaction. No method is disclosed.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a method for effectively utilizing carbon monoxide produced by another reaction, particularly carbon monoxide containing an ionic halogen compound without adversely affecting the reaction. An object of the present invention is to provide a novel method for producing dialkyl oxalate, which can produce dialkyl oxalate.

[0004]

The object of the present invention is to provide (1)
First step of introducing carbon monoxide and alkyl nitrite into a reactor and reacting in the presence of a platinum group metal catalyst to produce dialkyl oxalate and nitric oxide, (2) condensing the product of the first step To a condensate containing dialkyl oxalate and a non-condensable gas containing nitric oxide.
And (3) introducing the non-condensable gas of the second step to the regeneration tower, treating the carbon monoxide containing the ionic halogen compound with alkali to introduce the non-condensable gas into molecular oxygen and alkyl alcohol. To regenerate the nitric oxide in the non-condensed gas into alkyl nitrite, and supply the regenerated gas and the carbon monoxide to the reactor in the first step. Is solved by the method for producing a dialkyl oxalate.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, in the first step, dialkyl oxalate and nitric oxide are produced by reacting carbon monoxide and alkyl nitrite in a reactor. This reaction can be performed in a gas phase or a liquid phase, but is preferably carried out in a gas phase industrially. Then, in a second step, by condensing the product of the first step in a condenser,
A condensate containing dialkyl oxalate and a non-condensable gas containing nitric oxide are separated.

In the third step, the non-condensable gas is brought into contact with molecular oxygen and alkyl alcohol in the regeneration tower (reacting nitrogen monoxide in the non-condensable gas with molecular oxygen and alkyl alcohol). The alkyl nitrite is regenerated. The gas (regeneration gas) containing the alkyl nitrite is supplied to the first step as a raw material for producing dialkyl oxalate. In the present invention, in the third step, carbon monoxide produced by another reaction, particularly carbon monoxide containing an ionic halogen compound produced by another reaction is alkali-treated and introduced into a regeneration tower, It is effectively reused in the first step as a raw material for producing dialkyl oxalate.

The alkyl nitrite comprises, for example, an alkyl group comprising methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, pentyl, hexyl. And lower alkyl groups having 1 to 6 carbon atoms. As the alkyl nitrite, alkyl nitrite having 1 to 4 carbon atoms such as methyl nitrite, ethyl nitrite, n-propyl nitrite, i-propyl nitrite, n-butyl nitrite, i-butyl nitrite is preferable. Of these, methyl nitrite is particularly preferred. Further, as the above-mentioned alkyl alcohol, an alkyl alcohol which is a component of these alkyl nitrites is used.

Next, each step of the present invention will be described in detail with reference to a flow sheet (FIG. 1) showing one embodiment of the present invention. The platinum group metal catalyst used in the first step is preferably a platinum group metal or a compound thereof,
The platinum group metal compound is preferably reduced and used in the form of a platinum group metal (Japanese Patent Publication No. 61-6057,
Japanese Patent Publication No. 26977/1986). Examples of the platinum group metal include platinum metal, palladium metal, rhodium metal, iridium metal and the like, and examples of the compound include inorganic acid salts (nitrate, sulfate,
Phosphates, etc., halides (chlorides, bromides, etc.), organic acid salts (acetates, oxalates, benzoates, etc.), complexes and the like are used. Among the platinum group metals or their compounds,
Palladium metal or its compounds are particularly preferred.

As the palladium compound, for example, inorganic salts of palladium (palladium nitrate, palladium sulfate,
Palladium phosphate, etc.), halides of palladium (palladium chloride, palladium bromide, etc.), organic acid salts of palladium (palladium acetate, palladium oxalate, palladium benzoate, etc.), or complexes of palladium (alkyl phosphines, such as trimethylphosphine) , An arylphosphine such as triphenylphosphine, an alkylarylphosphine such as diethylphenylphosphine, or an arylphosphite such as triphenylphosphite as a ligand).

The platinum group metal catalyst is supported on an inert carrier, preferably 0.01 to 10% by weight, more preferably 0.2 to 2% by weight, in terms of platinum group metal. It is industrially preferred to use it in the form of a solid catalyst. For example, palladium metal or a compound thereof is activated carbon, alumina (such as α-alumina), silica, diatomaceous earth, pumice, zeolite, molecular sieve,
It is preferable that the carrier is supported on an inert carrier such as spinel in the above-described amount. When using a solid catalyst in which the platinum group metal compound is supported on a carrier, the supported platinum group metal compound is used by being reduced to a platinum group metal with a reducing substance such as hydrogen in advance, or before the reaction. It is preferable to use it after reducing it to a platinum group metal with a reducing substance such as carbon monoxide in a reactor. The platinum group metal catalyst is prepared by a known method (impregnation method, evaporation to dryness method, etc.).

The platinum group metal catalyst used in the first step can contain, for example, iron or a compound thereof (JP-A-59-80630). Examples of iron or its compounds include metallic iron, iron (II) compounds and iron (III) compounds. As the iron (II) compound, for example, ferrous sulfate, ferrous nitrate, ferrous chloride, ammonium ferrous sulfate, ferrous lactate, ferrous hydroxide and the like are used, and iron (III)
As the compound, ferric sulfate, ferric nitrate, ferric chloride, ammonium ferric sulfate, ferric lactate, ferric hydroxide, ferric citrate and the like are used. The iron or a compound thereof preferably has a platinum group metal: iron (atomic ratio) of 1000 or more.
0: 1 to 1: 4, more preferably 5000: 1 to 1: 3
Used to be in the range. The catalyst containing iron or its compound is prepared by a known method.

The carbon monoxide used in the first step may be pure, but may be diluted with an inert gas such as nitrogen, or may contain a small amount of hydrogen gas or methane. Further, in the present invention, in order to compensate for the carbon monoxide consumed in the first step and the carbon monoxide lost by purging of the circulating gas, carbon monoxide generated by another reaction, particularly one containing an ionic halogen compound, is used. Carbon oxide is also subjected to alkali treatment, introduced into the regeneration tower in the second step, and can be used in the first step.

In the first step, carbon monoxide and alkyl nitrite
If the reaction is a gas phase method, for example, as shown in FIG.
Feeds a source gas containing carbon monoxide and alkyl nitrite
11 into the reactor 1 and the platinum group metal catalyst and the gas phase
(Japanese Patent Publication No. 61-60)
No. 57, Japanese Patent Publication No. 61-26977, etc.). This
, The contact time between the source gas and the platinum group metal catalyst is 10
Seconds or less, more preferably 0.2 to 5 seconds.
The reaction temperature is 50-200 ° C, and more preferably 80-150 ° C
Is preferred. The reaction pressure is from normal pressure to 10 kg /
cm^TwoG, and from normal pressure to 5kg / cm^TwoIn the range of G
Preferably 2 to 5 kg / cm ^TwoIn the range of G
More preferably. The reactor is a single tube
A heat exchanger type reactor of the type or a multi-tube type is effective.

The concentration of carbon monoxide in the raw material gas is 2 to
It is selected in the range of 90% by volume. Although the concentration of alkyl nitrite in the raw material gas can be changed in a wide range, in order to obtain a satisfactory reaction rate, the alkyl nitrite must be present so that the concentration in the raw material gas becomes 1% by volume or more. Is preferred. The concentration of the alkyl nitrite in the source gas is selected, for example, in the range of 5 to 30% by volume.

As described above, in the first step, oxalic acid
A product containing dialkyl (eg, a reaction gas) is obtained.
Can be Then, in a second step, the product (for example,
Reaction gas) through conduit 12 to the bottom of condenser 2 (absorption tower).
To the temperature at which dialkyl oxalate is condensed
Condensate containing dialkyl oxalate and nitric oxide
Is separated into non-condensable gases containing sulfur. At this time,
To prevent dialkyl oxalate from being entrained in non-condensable gas
The product is then passed through conduit 13
Below the boiling point of the alcohol while in contact with
It is preferable to cool and absorb at the above temperature. For example,
When the target substance is dimethyl oxalate, the product is 100
Part of methanol at 30-60 ° C 0.001-0.1 volume
It is preferable to make contact with the part. The operating pressure in the second step is
From normal pressure to 10kg / cm^TwoG, and from normal pressure to 5kg /
cm ^TwoG is preferably in the range of 2 to 5 kg /
cm^TwoMore preferably, it is in the range of G. The second
As the alkyl alcohol in the process, alkyl nitrite
The constituent alkyl alcohol is used.

Next, the non-condensed gas in the second step contains, in addition to unreacted carbon monoxide and alkyl nitrite, nitric oxide generated in the first step. To the third step of regeneration. In the third step, the non-condensed gas is led to the bottom of the regenerator 3 through the conduit 14 and brought into contact with molecular oxygen supplied through the conduit 17 and alkyl alcohol supplied through the conduit 19 (to convert nitrogen monoxide into molecular Reacting with oxygen and a lower alcohol) to regenerate the alkyl nitrite. Then, an ester-containing nitrite-containing gas (regeneration gas) derived from the regeneration tower 3 is supplied to the first step through the conduit 20 and reused. Further, the water generated by the regeneration is extracted from the regeneration tower through the conduit 21 together with the alkyl alcohol. The alkyl alcohol containing water can be purified by distillation and reused as the alkyl alcohol used in the second and third steps. As described above, as the alkyl alcohol in the third step, an alkyl alcohol which is a component of alkyl nitrite is used.
As molecular oxygen, oxygen gas or air is used. In addition, as a regeneration tower, a normal gas-liquid contacting device such as a packed tower, a bubble tower, a spray tower, and a step tower is used.

In the above-mentioned regeneration of alkyl nitrite,
The reaction is controlled so that the concentration of nitric oxide in the regeneration gas becomes 2 to 7% by volume. For this reason, with respect to 1 mol of nitrogen monoxide in the non-condensed gas introduced into the regeneration tower, 0.08 to 0.2 mol of molecular oxygen is supplied, and the boiling point of the alkyl alcohol is not more than the boiling point of the pressure at the time of regeneration It is preferred to contact the non-condensable gas with molecular oxygen and the alkyl alcohol at a temperature (eg, from 0 ° C. to the boiling point of the alkyl alcohol). The supply amount of the alkyl alcohol is preferably 1 to 5 parts by volume with respect to 1 part by volume of nitrogen monoxide in the non-condensed gas, and the contact time is preferably 0.5 to 20 seconds.
The operating pressure is preferably from normal pressure to 10 kg / cm ² G, more preferably from normal pressure to 5 kg / cm ² G.
More preferably, it is cm ² G.

In the present invention, carbon monoxide generated by another reaction, particularly, carbon monoxide generated by another reaction is added to the regeneration tower in the third step.
The carbon monoxide containing the ionic halide is alkali treated and introduced through conduit 18. Then, without adversely affecting the reaction (manufacture of oxalic acid diester), it is supplied to the reactor in the first step together with the regeneration gas and is effectively reused. Examples of the ionic halogen compound include ionic chlorine compounds such as hydrogen chloride and chlorine.

As the carbon monoxide containing the ionic halogen compound, for example, an oxalic acid diester is subjected to a decarbonylation reaction in the presence of an organic phosphorus compound catalyst,
Carbon monoxide generated when a carbonate ester is produced is exemplified. Examples of the decarbonylation reaction of the oxalic acid diester include a reaction in which a diaryl oxalate is formed into a diaryl carbonate and carbon monoxide in the presence of an organic phosphorus compound catalyst according to the following reaction formula. The carbon monoxide produced by this reaction has high purity, but contains, for example, about 1 ppm by volume to 1% by volume of an ionic halogen compound depending on the reaction conditions and the type of catalyst. Furthermore, the carbon monoxide produced by this reaction also contains trace amounts of phenol and carbon dioxide, as the case may be.

[0020]

Embedded image (In the formula, Ar represents an aryl group such as a phenyl group and a naphthyl group.)

The carbon monoxide containing the ionic halogen compound is removed from the system by purging the carbon monoxide consumed in the reaction of the first step and the circulating gas in the gas circulation system via the reactor, the condenser and the regeneration tower. It is preferable that the gas is introduced into the bottom of the regeneration tower in the third step so as to compensate for the loss of carbon monoxide to the outside and maintain the raw material gas composition in the first step in a desired range. At the bottom of the regeneration tower, for example, the non-condensable gas of the second step may be introduced from the pipe 18 via the pipe 14 supplied to the third step, or may be separately introduced separately.

Further, in the present invention, it is preferable that carbon monoxide containing an ionic halogen compound is treated with alkali and introduced into the bottom of the regeneration tower in the third step. Further, in the present invention, if necessary, before and / or after the alkali treatment, a treatment with an adsorbent such as activated carbon or alumina is performed to remove organic substances (such as nonionic halogen compounds) from the carbon monoxide. May be.

The alkali treatment is carried out by bringing carbon monoxide containing an ionic halogen compound into contact with an aqueous alkali solution or with an alkaline adsorbent. These may be performed alone or in combination, but a method of bringing them into contact with an alkaline aqueous solution is effective. Examples of the aqueous alkali solution include hydroxides and carbonates of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, and calcium carbonate. Is preferred. The concentration of these alkali metal or alkaline earth metal compounds is preferably about 1 to 50% by weight. Examples of the alkaline adsorbent include zeolite, magnesia, zinc oxide, activated carbon, and those on which a basic alkali metal compound or alkaline earth metal compound (including a metal) is supported.

The temperature of the alkali treatment is preferably 0 to 100 ° C., more preferably 10 to 50 ° C., and the pressure may be normal pressure or pressurization. The treatment (contact) time is not particularly limited as long as the ionic halogen compound contained in carbon monoxide can be effectively removed. In addition, as a device for the alkali treatment, a simple device such as a normal absorption tower or a scrubber can be used.

In the present invention, in order to compensate for the nitrogen component lost outside the system due to the purge of the circulating gas, the third
At the bottom of the regeneration tower of the process, alkyl nitrite, nitrogen oxides (nitrogen monoxide, nitrogen dioxide, nitrous oxide, nitrous oxide, etc.) or nitric acid are introduced through conduit 16. In this way, the gas containing the regenerated alkyl nitrite (regeneration gas) is supplied to the first step while the carbon monoxide is supplied and the nitrogen component is supplied as necessary.

The above decarbonylation reaction is preferably carried out in a liquid phase in the presence of an organic phosphorus compound catalyst. When the decarbonylation reaction is carried out in a liquid phase, the catalyst can be one which can carry out the decarbonylation reaction at a relatively low temperature (about 100 to 350 ° C.) and has a high selectivity (at least 50% or more, particularly 60%). -100%) are preferred.

The decarbonylation catalyst used in the liquid phase reaction includes, for example, a catalyst comprising an organic phosphorus compound, preferably an organic phosphorus compound having at least one carbon-phosphorus bond. Examples of such an organic phosphorus compound include phosphines (w), phosphine oxides (x), and phosphine dihalides (y) represented by formulas (w) to (z).
And a catalyst comprising at least one organic phosphorus compound selected from phosphonium salts (z).

[0028]

Embedded image

Wherein R ^{1 to} R ¹³ are an alkyl group having 1 to 16 carbon atoms, an aryl group having 6 to 16 carbon atoms, and
And X represents an atom or an atomic group capable of forming a counter ion, and Y ¹ and Y ² each represent a halogen atom such as a chlorine atom, a bromine atom, and an iodine atom. Show. Compounds (w) to (z)
Has at least one of the groups described above. ]

The groups represented by R ^{1 to} R ¹³ include:
For example, an alkyl group having 1 to 16 carbon atoms (methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, etc.) and an aryl group having 6 to 16 carbon atoms (phenyl group , A methylphenyl group, a methoxyphenyl group, a chlorophenyl group, a naphthyl group, a methylnaphthyl group, a methoxynaphthyl group, a chloronaphthyl group, etc., an aralkyl group having 7 to 22 carbon atoms (benzyl group, phenethyl group, 4-methylbenzyl group, 4-methoxybenzyl group,
p-methylphenethyl group).

The above-mentioned aryl group and aralkyl group are, as substituents directly bonding to the carbon forming the aromatic ring, an alkyl group having 1 to 16 carbon atoms, an alkoxy group having 1 to 16 carbon atoms, and a nitro group. And at least one selected from halogen atoms (fluorine, chlorine, bromine, etc.)
May have one or more substituents.

As the above-mentioned organic phosphorus compounds (w) to (z), those in which all of the groups (R ^{1 to} R ¹³ ) are all aryl groups are preferred.
) May be an aryl group, and the remainder may be an alkyl group or an aralkyl group.

Examples of the phosphine in which all of R ^{1 to} R ^{3 in} the formula (w) are aryl groups include triphenylphosphine, tris (4-chlorophenyl) phosphine, and tris (4-tolyl) phosphine.

Examples of the phosphine oxide in which all of R ^{4 to} R ^{6 in} the formula (x) are aryl groups include triphenylphosphine oxide, tris (4-chlorophenyl) phosphine oxide and tris (4-tolyl) phosphine oxide. No.

Examples of the phosphine dihalide in which all of R ^{7 to} R ^{9 in} the formula (y) are aryl groups include triphenylphosphine dichloride and triphenylphosphine dibromide. Among phosphine dihalides, triarylphosphine dichloride such as triphenylphosphine dichloride is preferable.

The phosphonium salt of the formula (z) includes R ¹⁰
To R ¹³ are all aryl groups and a counter ion X
^A phosphonium salt in which-is a halogen ion, an aliphatic carboxylate ion or a fluoroborate ion is preferred, but 1 to 3, especially 2 to 3 of R ^{10 to} R ¹³ are aryl groups, and Is an aralkyl group or an alkyl group, and the counter ion X ⁻ may be a halogen ion, an aliphatic carboxylate ion, a fluoroborate ion, or the like.

Examples of the phosphonium salt in which all of R ^{10 to} R ^{13 in} the formula (z) are aryl groups include, for example, tetraphenylphosphonium chloride, tetraphenylphosphonium bromide, tetraphenylphosphonium iodide, 4-chlorophenyltriphenylphosphonium chloride , 4-chlorophenyl triphenylphosphonium bromide, 4-ethoxyphenyl triphenyl phosphonium chloride, 4-ethoxyphenyl triphenylphosphonium bromide, 4-methylphenyl triphenyl phosphonium chloride, 4-methylphenyl triphenylphosphonium bromide and the like of the counterion X ^- Is a halogen ion, and the like.

Among the above organic phosphorus compounds, tetraaryl phosphonium salts are preferred. Among them, tetraarylphosphonium halide is more preferable, and among them, tetraarylphosphonium chloride such as tetraphenylphosphonium chloride is particularly preferable. The decarbonylation catalyst comprising an organic phosphorus compound may be used alone or as a mixture of two or more kinds, and may be uniformly dissolved and / or suspended in the reaction solution. The amount of the organic phosphorus compound used in the decarbonylation reaction is 0.001 to 50 mol%, and more preferably 0.01 to 50 mol% based on the oxalic acid diester.
It is preferably about 1 to 20 mol%.

It is preferable that an inorganic or organic halogen compound-based additive is added to the above-mentioned decarbonylation catalyst comprising an organic phosphorus compound, if necessary. When phosphine or phosphine oxide is used as the organic phosphorus compound, or when a phosphonium salt other than halide and hydrogendihalide is used, it is preferable to add the halogen compound-based additive. The added halogen compound-based additive is added in an amount of 0.1 to the organic phosphorus compound.
It is preferably about 01 to 150 times, more preferably about 0.05 to 100 times.

Examples of the inorganic halogen compound-based additives include aluminum halides (aluminum chloride, aluminum bromide, etc.), platinum group metal halides (platinum chloride, ruthenium chloride, palladium chloride, etc.), and phosphorus halides (pentahedral). Phosphorus chloride), sulfur halide (such as thionyl chloride), hydrogen halide (such as hydrogen chloride), and halogen alone (such as chlorine).

As the organic halogen compound-based additive, alkyl halides (chloroform, carbon tetrachloride,
1,2-dichloroethane, butyl chloride, etc.), aralkyl halides (benzyl chloride, etc.), halogen-substituted aliphatic carboxylic acids (chloroacetic acid, bromoacetic acid, etc.), acid halides (oxalyl chloride, propionyl chloride, benzoyl chloride, etc.), etc. Is mentioned. As the organic halogen compound, a compound having a structure in which a halogen atom is bonded to a saturated carbon (C-Hal) or a structure in which a halogen atom is bonded to a carbonyl carbon (CO-Hal) is preferable. is there. Here, Hal represents a halogen atom such as a chlorine atom and a bromine atom.

In the decarbonylation reaction, for example, a diaryl oxalate and a catalyst containing an organic phosphorus compound as main components (and a halogen compound-based additive as necessary) are supplied to a reactor to remove generated carbon monoxide. Meanwhile, the diaryl oxalate is subjected to a decarbonylation reaction in a liquid phase to produce a diaryl carbonate. At this time, the reaction temperature is preferably 100 to 450 ° C, more preferably 160 to 400 ° C, particularly preferably 180 to 350 ° C. Further, the reaction pressure is not particularly limited, for example, 10 mmH
g~10kg / cm ² may be in the range of G, but considering the introduction of generated carbon monoxide to the regenerator in the third step, 10 kg / cm ² G from atmospheric pressure, even from normal pressure It is preferably in the range of 5 kg / cm ² G, particularly preferably in the range of ^{2 to} 5 kg / cm ² G.

As described above, carbon monoxide produced by another reaction (for example, decarbonylation reaction of diaryl oxalate), particularly carbon monoxide containing an ionic halogen compound, can be produced without adversely affecting the reaction. The dialkyl oxalate can be produced continuously with effective recycling (ie, without causing a reduction in catalyst activity or selectivity).

The dialkyl oxalate is separated and recovered from the condensate of the second step, which is extracted from the condenser 2 through the conduit 15, by distillation or the like. In this operation, since the condensate contains a small amount of by-products such as dialkyl carbonate and alkyl formate, in addition to the target product dialkyl oxalate, for example, by conducting the condensate to a distillation column and distilling by a normal operation Done.

[0045]

Next, the present invention will be described in detail with reference to examples and comparative examples. The analysis was performed by gas chromatography. The space-time yield (STY: g / L · hr) and selectivity (%) of dimethyl oxalate (DMO) were determined by the following equations. Here, L indicates liter.

[0046]

(Equation 1)

[0047]

(Equation 2) (Where a is dimethyl oxalate, b is dimethyl carbonate, c
Represents the number of moles of carbon dioxide produced. )

Reference Example 1 [Production of dimethyl oxalate] Inner diameter 27.1 mm, height 5
A solid catalyst in which 0.5% by weight of palladium (metal) was supported on pelletized α-alumina (diameter 5 mm, length 3 mm) was packed in a stainless steel reactor consisting of a 00 mm tube. After maintaining the temperature of the catalyst layer at 103 to 115 ° C. by passing hot water through the shell side of the reactor, the raw material gas (composition) pre-heated to 90 ° C. by a heat exchanger by a diaphragm gas circulation pump from the upper part of the catalyst layer : Carbon monoxide 2
2.0% by volume, methyl nitrite 10.0% by volume, nitric oxide 4.0% by volume, methanol 5.2% by volume, carbon dioxide 1.7% by volume, nitrogen 57.1% by volume). 15Nm
Dimethyl oxalate was produced at a supply rate of ³ / hr at 2 kg / cm ² G.

The gas that passed through the catalyst layer was converted into a gas-liquid contact absorption tower filled with Raschig rings (inner diameter 43 mm, height 1000
mm), and was brought into countercurrent contact with 0.42 L / hr of methanol introduced from the top at about 35 ° C (top temperature 30 ° C, bottom temperature 40 ° C). And 0.3 kg / hr of condensate (composition: dimethyl oxalate 42.6% by weight, dimethyl carbonate 1.8% by weight, methyl formate 0.03% by weight, methanol 42.6% by weight) was obtained from the bottom of the column. From the top, a non-condensable gas (composition: carbon monoxide 16.2% by volume,
4.9% by volume of methyl nitrite, 8.1% by volume of nitric oxide,
15.9% by volume of methanol, 1.8% by volume of carbon dioxide,
(Nitrogen 53.1% by volume) 1.23 Nm ³ / hr was obtained. The STY of dimethyl oxalate was 450 g / L · hr, and the selectivity was 96.3%.

The non-condensed gas contains 13.8 NL / hr of oxygen.
And a gas mixture of 0.5 NL / hr of nitric oxide and a gas-liquid contact regeneration tower (inner diameter 83 mm, height 1000 m)
m), the mixture was brought into countercurrent contact with 0.33 L / hr of methanol introduced from the top of the column at a top temperature of 30 ° C. and a bottom temperature of 40 ° C. to regenerate nitric oxide in the gas to methyl nitrite. did. Regeneration gas derived from the top of the regeneration tower (composition:
(18.2% by volume of carbon monoxide, 10.4% by volume of methyl nitrite, 4.2% by volume of nitric oxide, 5.4% by volume of methanol, 2.0% by volume of carbon dioxide, 53.0% by volume of nitrogen)
1.1 Nm ³ / hr is led to the circulation pump to 2.1 Nm ³ / hr.
kg / cm ² G, pressurized to 49 NL / hr of carbon monoxide
(2.1 kg / cm ² G) and then supplied to the reactor. As a result, the reaction results were stable for a long time (200 hours or more). 4. derived from the bottom of the regeneration tower
0.48 L / hr of methanol containing 7% by weight of water
Was used as a methanol source in the regeneration tower after removing water by distillation.

On the other hand, the above-mentioned condensate is stored for 50 hours, and is stored in a distillation column (inner diameter 150 mm, height 7500 m
m, the column bottom volume was 100 L), and the batch distillation was performed (column temperature 140 ° C., pressure 350 mmHg), and the purity was 99.9.
5.8 kg by weight of dimethyl oxalate were obtained.

Reference Example 2 [Production of diphenyl carbonate] 1.5 mol% of tetraphenylphosphonium chloride was added to diphenyl oxalate.
The mixture was heated to 150 ° C. for dissolution. This liquid was transferred to a device in which two glass reactors (internal volume 1 L) each equipped with a thermometer, a stirrer, and an overflow tube were connected by using a metering pump.
The reactor was supplied at 00 mL / hr, and the two reactors were heated with a mantle heater and maintained at 230 ° C. to carry out a decarbonylation reaction of diphenyl oxalate. The overflow position of each reactor was 600 mL. Supply start 2
After 0 hour, the composition of the overflow solution (reaction solution of the decarbonylation reaction) in the second reactor was 14.1 diphenyl oxalate.
6% by weight and 85.1% by weight of diphenyl carbonate, and the amount was about 270 mL / hr. The composition of the gas generated from each reactor was about 100% of carbon monoxide, and the amount was 25 NL / hr. However, this gas contained 200 ppm by volume of an ionic chlorine compound and 120 ppm by volume of a nonionic chlorine compound as impurities.

Example 1 [Production of dimethyl oxalate] After the pressure of 25 NL / hr of carbon monoxide generated in the decarbonylation reaction of Reference Example 2 was increased to 2.1 kg / cm ² G by a diaphragm compressor, 5 m
packed tower (inner diameter 32 m)
m, height 450 mm). From the top of the tower, a 5% by weight aqueous sodium hydroxide solution was added at 200 ml / hr.
And contacted the gas. Next, 25 NL / hr of carbon monoxide (2.1 kg / cm
² G) other supplied to the bottom of the gas-liquid contact type regeneration column of Example 1 was prepared dimethyl oxalate in the same manner as in Reference Example 1. However, carbon monoxide 24 NL / hr (2.1 kg / c
m ² G) was supplied to the regeneration gas. As a result, dimethyl oxalate could be produced for a long time (200 hours or more) with the same reaction results as in Reference Example 1.

COMPARATIVE EXAMPLE 1 [Production of dimethyl oxalate] The pressure of 25 NL / hr of carbon monoxide generated in the decarbonylation reaction of Reference Example 2 was increased to 2.1 kg / cm ² G by a diaphragm type compressor to obtain carbon monoxide. Dimethyl oxalate was produced in the same manner as in Reference Example 1, except that the regeneration gas derived from the regeneration tower was supplied together with 24 NL / hr (2.1 kg / cm ² G). As a result, in the initial stage (about 50 hours) after the supply of carbon monoxide generated by the decarbonylation reaction was started, the reaction results were the same as those in Example 1, but thereafter the activity gradually decreased and the selectivity also increased. Dropped. That is, 50 hours after the start of the supply, the STY of dimethyl oxalate was 450 g / L · hr, and the selectivity was 96.3%.
However, after 200 hours, the STY was 320 g / L · h.
r, the selectivity became 93.7%.

Comparative Example 2 [Production of dimethyl oxalate] After the pressure of 25 NL / hr of carbon monoxide generated in the decarbonylation reaction of Reference Example 2 was increased to 2.1 kg / cm ² G by a diaphragm compressor, 5 m
packed tower (inner diameter 32 m)
m, height 450 mm). From the top of the tower, a 5% by weight aqueous sodium hydroxide solution was added at 200 ml / hr.
And contacted the gas. Next, 25 NL / hr of carbon monoxide (2.1 kg / cm
² G) is converted to 24 NL / hr of carbon monoxide (2.1 kg / c
Dimethyl oxalate was produced in the same manner as in Reference Example 1, except that the regeneration gas supplied from the regeneration tower together with m ² G) was supplied. As a result, by-products of carbon dioxide increased from the beginning of the supply of carbon monoxide generated by the decarbonylation reaction, and the selectivity of dimethyl oxalate also decreased to 93.6%. The STY of dimethyl oxalate slightly decreased at 435 g / L · hr, but was maintained for a long time.

[0056]

According to the present invention, dialkyl oxalate is produced while effectively utilizing carbon monoxide produced by another reaction, particularly carbon monoxide containing an ionic halogen compound, without adversely affecting the reaction. can do. That is, according to the present invention, a dialkyl oxalate can be continuously produced while maintaining a high space-time yield and effectively suppressing a decrease in the selectivity and maintaining a high selectivity. The present invention, for example, recovers carbon monoxide removed to the outside of the reaction system by a decarbonylation reaction of diaryl oxalate and re-uses the production of dialkyl oxalate without causing a decrease in catalytic activity or a decrease in selectivity. Can be used. Furthermore, in the present invention, since phenol and carbon dioxide in the carbon monoxide can be removed, contamination of impurities in the production process of dialkyl oxalate can be suppressed, adverse effects in the reaction and separation and purification can be reduced, and inertness can be reduced. An increase in gas can also be suppressed. The method of the present invention is an industrially excellent method for producing dialkyl oxalate.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an embodiment of the present invention.

[Explanation of symbols]

1 is a reactor, 2 is a condenser, 3 is a regeneration tower, and 11 to 2
1 indicates a conduit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C07B 61/00 300 C07B 61/00 300

Claims (4)

[Claims] 1. A first step in which carbon monoxide and alkyl nitrite are introduced into a reactor and reacted in the presence of a platinum group metal catalyst to produce dialkyl oxalate and nitric oxide. A second step of introducing the product of the first step to a condenser to separate it into a condensate containing dialkyl oxalate and a non-condensable gas containing nitric oxide; (3) regenerating the non-condensable gas of the second step While leading to the tower, carbon monoxide containing an ionic halogen compound is alkali-treated and introduced into the regeneration tower, and the non-condensable gas is brought into contact with molecular oxygen and alkyl alcohol to remove nitrogen monoxide in the non-condensable gas. A process for producing a dialkyl oxalate, comprising the steps of a third step of regenerating alkyl nitrite and supplying the regenerated gas and the carbon monoxide to the reactor of the first step. 2. The carbon monoxide containing an ionic halogen compound is carbon monoxide generated when an oxalic acid diester is subjected to a decarbonylation reaction in the presence of an organic phosphorus compound catalyst to form a carbonate. Item 10. The method for producing a dialkyl oxalate according to Item 1. 3. The method for producing a dialkyl oxalate according to claim 2, wherein a decarbonylation reaction is carried out by adding a halogen compound-based additive. 4. The method for producing a dialkyl oxalate according to claim 1, wherein the ionic halogen compound is an ionic chlorine compound.